Hi Skip: What you have is a case of "waterway smile," as we called it in Charleston, SC. It's caused by tannic acid from oak leaves that fall into the water. You can use fancy cleaners if you want, but if you can find it, you can use a mild solution of straight oxalic acid. I bought a bag at Ross Marine in Charleston when I last hauled out... I believe it was a few bucks for a big plastic bag of crystals... but this was probably fifteen years ago. I dissolved about a quarter cup of crystals in a gallon of water, brushed on, and the stain faded before I had a chance to scrub. I understand it work well on rust stains and blood, too. Try the boatyards near the harbor (if there are any left) or a janitorial service company that services the industry. It's possible that oxalic is the main ingredient in "oxy-clean" and other household cleaners, but then you're paying for labels and packaging. Good luck. If you try to find it, let me know what you discover. Best BG -- Brian Gilbert Author, Fix It And Sail, The Complete Trailer-Sailor Marine Media 3404 Hartford Dr Chattanooga, TN 37415 From: montgomery_boats-request@mailman.xmission.com Reply-To: montgomery_boats@mailman.xmission.com Date: Mon, 07 May 2007 11:41:16 -0600 To: montgomery_boats@mailman.xmission.com Subject: montgomery_boats Digest, Vol 51, Issue 4 David, It is definitely a stain. It reminds me of tea stains inside your favorite morning mug. I'll give your suggestions a try later this week. It's tough getting to West Marine on a week night after work. Thanks, Skip